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Lotfi BOUCHERIT
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BAD_ADDRESS in failover dhcp (windows server 2016)

hello,
we have a failover dhcp server composed of two windows server 2016 standard vms.
lately, we notice frequently that ip addresses become marqued as BAD_ADDRESS and computers that were holding these ip addresses cannot get another valid ip address,
we discovered that some support guys, set manually network configuration for some computers (that become BAD_ADDRESS), and those ip addresses are in dhcp scopes, which makes a part of computers disconnect from network.
when I tried to reproduce this problem in a newly installed lab, I find that the address becomes BAD_ADDRESS but the client gets another IP address,
I would like to know what could prevent dhcp servers from acting correctly and not handling ip address for client after detecting BAD_ADDRESS in network.
thank you
DHCPWindows 10AzureWindows Server 2016

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Seth Simmons

8/22/2022 - Mon
Lotfi BOUCHERIT

ASKER
I would like to add, that I tested and observed the process of requesting network configuration in windows 10 client using Wireshark, and found that the communication and the DORA process is run correctly but the received ip address from the server is not applied to computer,
arnold

Bad_address points to a conflicted address, I.e. The DHCP has an ip to allocate, but it is in use.
Aaron Tomosky

Enable conflict detection (I always set to 2 as habbit)
https://www.oreilly.com/library/view/windows-server-cookbook/0596006330/ch14s05.html
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William Peck
fred hakim

The DHCP server should be configured with an address range, say  10.10.1.100 to 10.10.1.199.  If your techs need to define static addresses, they should be outside the range defined in the DHCP server, but still within the desired subnet, say 10.10.1.20 or 10.10.1.201.  

The second issue involves where the DHCP server lives.  If  its an enabled role within the windows server, then with two servers, each should be configured for different ranges of IP addresses.  If the DHCP server is in the router, then make sure those roles are turned off in the windows servers.
arnold

The person has a 2016 DHCP server configured in failover.

the issue can be the allocation range includes one device that was set statically.
Pete Long

I had this last week :(


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arnold

Not sure without a failover why the node was issuing IPs.

You could exclude a block of IPs on the current one, than on the secondary allow only this block to be allocated while all the rest of the block from the primary be excluded.
fred hakim

@ Arnold  

I think I just said that....  If  its an enabled role within the windows server, then with two servers, each should be configured for different ranges of IP addresses.
arnold

Yes, to achieve the same result. it would leave the user to interpret how to implement
mine is just same scope exclude a block on one, while that is the only block allocated by the other.
Your help has saved me hundreds of hours of internet surfing.
fblack61
fred hakim

Actually, Lotfi BOUCHERIT's solution to break their high availability functionality just covers up their problem at the expense of the functionality (which he noted needs to be reimplemented) . One solution, to reserve blocks of addresses to prevent overlapping,  should preserve their high availability functionality.  That solution was provided by myself and Arnold.
Seth Simmons

No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

Accept: 'Lotfi BOUCHERIT' (https:#a43027388)

If you feel this question should be closed differently, post an objection and the moderators will review all objections and close it as they feel fit. If no one objects, this question will be closed automatically the way described above.

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